@article{FranzSudoKhomenko2022, author = {Franz, Gerhard and Sudo, Masafumi and Khomenko, Vladimir}, title = {40Ar/39Ar dating of a hydrothermal pegmatitic buddingtonite-muscovite assemblage from Volyn, Ukraine}, series = {European journal of mineralogy : EJM : an international journal on mineralogy, petrology, geochemistry, and related sciences}, volume = {34}, journal = {European journal of mineralogy : EJM : an international journal on mineralogy, petrology, geochemistry, and related sciences}, number = {1}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {0935-1221}, doi = {10.5194/ejm-34-7-2022}, pages = {7 -- 18}, year = {2022}, abstract = {We determined Ar-40/Ar-39 ages of buddingtonite, occurring together with muscovite, with the laser-ablation method. This is the first attempt to date the NH4-feldspar buddingtonite, which is typical for sedimentary-diagenetic environments of sediments, rich in organic matter, or in hydrothermal environments, associated with volcanic geyser systems. The sample is a hydrothermal breccia, coming from the Paleoproterozoic pegmatite field of the Korosten Plutonic Complex, Volyn, Ukraine. A detailed characterization by optical methods, electron microprobe analyses, backscattered electron imaging, and IR analyses showed that the buddingtonite consists of euhedral-appearing platy crystals of tens of micrometers wide, 100 or more micrometers in length, which consist of fine-grained fibers of <= 1 mu m thickness. The crystals are sector and growth zoned in terms of K-NH4-H3O content. The content of K allows for an age determination with the Ar-40/Ar-39 method, as well as in the accompanying muscovite, intimately intergrown with the buddingtonite. The determinations on muscovite yielded an age of 1491 +/- 9 Ma, interpreted as the hydrothermal event forming the breccia. However, buddingtonite apparent ages yielded a range of 563 +/- 14 Ma down to 383 +/- 12 Ma, which are interpreted as reset ages due to Ar loss of the fibrous buddingtonite crystals during later heating. We conclude that buddingtonite is suited for Ar-40/Ar-39 age determinations as a supplementary method, together with other methods and minerals; however, it requires a detailed mineralogical characterization, and the ages will likely represent minimum ages.}, language = {en} } @article{WilkeO'BrienGerdesetal.2010, author = {Wilke, Franziska Daniela Helena and O'Brien, Patrick J. and Gerdes, Axel and Timmerman, Martin Jan and Sudo, Masafumi and Khan, M. Ahmed}, title = {The multistage exhumation history of the Kaghan Valley UHP series, NW Himalaya, Pakistan from U-Pb and Ar-40/Ar- 39 ages}, issn = {0935-1221}, doi = {10.1127/0935-1221/2010/0022-2051}, year = {2010}, abstract = {Amphibole and mica Ar-40/Ar-39 ages as well as zircon, rutile and titanite U-Pb geochronology of eclogites and associated host rocks from the Higher Himalayan Crystalline Nappes (Indian Plate) in the Upper Kaghan Valley, Pakistan allow distinction of a multistage exhumation history. An Eocene age for peak-pressure metamorphism has been obtained by phengite Ar-40/Ar-39 (47.3 +/- 0.3 Ma) and zircon U-Pb (47.3 +/- 0.4 and 47.4 +/- 0.3 Ma) ages from cover and basement gneisses. A very short-lived metamorphic peak and rapid cooling is documented by an amphibole Ar-40/Ar-39 age of 46.6 +/- 0.5 Ma and a rutile U-Pb age of 44.1 +/- 1.3 Ma from eclogites. Phengite and biotite ages from cover and basement sequences metamorphosed during the Himalayan orogeny are 34.5 +/- 0.2 to 28.1 +/- 0.2 Ma whereas youngest biotites, yielding 23.6 +/- 0.1 and 21.7 +/- 0.2 Ma, probably reflect argon partial resetting. The amphibole age, together with those derived from phengite and zircon demonstrate a rate of initial exhumation of 86-143 mm/a i.e. an extremely rapid transport of the Indian Plate continental crust from ultra-high pressure (UHP) conditions back to crustal levels (47-46 Ma for transport from 140 to 40 km depth). Subsequent exhumation (46-41 Ma, 40-35 km) slowed to about 1 mm/a at the base of the continental crust but increased again later towards slightly higher exhumation rates of ca. 2 mm/a (41-34 Ma, 35- 20 km). This indicates a change from buoyancy-driven exhumation at mantle depths to compression forces related to continent-continent collision and accompanied crustal folding, thrusting and stacking that finally exposed the former deeply-buried rocks.}, language = {en} } @article{BachmannOnckenGlodnyetal.2009, author = {Bachmann, Raik and Oncken, Onno and Glodny, Johannes and Seifert, Wolfgang and Georgieva, Viktoria and Sudo, Masafumi}, title = {Exposed plate interface in the European Alps reveals fabric styles and gradients related to an ancient seismogenic coupling zone}, issn = {0148-0227}, doi = {10.1029/2008jb005927}, year = {2009}, abstract = {We present observations from a continuous exposure of an ancient plate interface in the depth range of its former seismogenic zone in the central Alps of Europe related to Late Cretaceous-early Tertiary subduction and accretion of the South Penninic lower plate underneath the Adriatic upper plate. The material forming the exposed plate interface zone has experienced flow and fracturing over an extended period of time followed by syncollisional exhumation, thus reflecting a multistage evolution. Fabric formation and metamorphism, however, chiefly record the deformation conditions of the precollisional setting along the plate interface. We identify an unstable slip domain from pseudotachylytes occurring in the temperature range between 200 and 300 degrees C. This zone coincides with a domain of intense veining in the subduction melange with mineral growth into open cavities, indicating fast, possibly seismic, rupture. Evidence for transient near-lithostatic fluid pressure as well as brittle fractures competing with mylonitic shear zones continues into the region below the occurrence of pseudotachylytes, possibly reflecting a zone of conditionally stable slip. The zone above the unstable slip area is devoid of veins but displays ample evidence of fluid-assisted processes similar to the deeper zone: solution-precipitation creep and dehydration reactions in the melange matrix, hydration, and sealing of the base of the upper plate. Seismic rupture here is possibly expressed by ubiquitous localized deformation zones. We hypothesize that trenchward sealing of parts of the plate interface as well as reaction-enhanced destruction of upper plate permeability is an important component, localizing the unstable slip zone. This relation may result from the competition of the pervasive, presumably interseismic, pressure solution creep destroying permeability and building elevated fluid pressure until the strength threshold is reached with seismic failure.}, language = {en} } @article{GuzmanPetrinovicBrodetal.2011, author = {Guzman, S. and Petrinovic, I. A. and Brod, J. A. and Hongn, Fernando D. and Seggiaro, R. E. and Montero, C. and Carniel, Roberto and Dantas, E. L. and Sudo, Masafumi}, title = {Petrology of the Luingo caldera (SE margin of the Puna plateau) a middle Miocene window of the arc-back arc configuration}, series = {Journal of volcanology and geothermal research}, volume = {200}, journal = {Journal of volcanology and geothermal research}, number = {3-4}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0377-0273}, doi = {10.1016/j.jvolgeores.2010.12.008}, pages = {171 -- 191}, year = {2011}, abstract = {We describe the petrographic characteristics, whole-rock geochemistry and mineral chemistry of rocks from the Pucarilla-Cerro Tipillas Volcanic Complex with emphasis on the rocks belonging to the middle Miocene Luingo caldera, located in the south-eastern portion of the Central Volcanic Zone (CVZ) of the Andes. We modelled the petrogenesis of the Luingo caldera rocks as a mixture of ca. 20\% crustal magmas and 80\% of mantle magmas by AFC with recharge processes. A comparison of Luingo geochemical data with the composition of Miocene-Pliocene volcanic rocks from the broad area, points to major thickening events during the middle Miocene for the western portion and during the upper Miocene for the eastern portion of the Southern CVZ. In the eastern sector (similar to 66 degrees W) the mantle source appears to change from a spinel-lherzolite type for the middle Miocene to a garnet-lherzolite type for the upper Miocene-Pliocene magmas. The areal distribution of the volcanic products led to the recognition of approximately equivalent areas covered by volcanic rocks both in the eastern and in the western Puna borders. This indicates a broad arc, which was structurally controlled at the proto-Puna/Puna margins, whose geochemical differences are related with variations in crustal thicknesses and heterogeneous mantle sources from west to east.}, language = {en} } @article{CarrapaDeCellesReinersetal.2009, author = {Carrapa, Barbara and DeCelles, Peter G. and Reiners, Peter W. and Gehrels, George E. and Sudo, Masafumi}, title = {Apatite triple dating and white mica Ar-40/Ar-39 thermochronology of syntectonic detritus in the Central Andes : a multiphase tectonothermal history}, issn = {0091-7613}, doi = {10.1130/G25698a.1}, year = {2009}, abstract = {We applied apatite U-Pb, fission track, and (U-Th)/He triple dating and white mica Ar-40/Ar-39 thermochronology to syntectonic sedimentary rocks from the central Andean Puna plateau in order to determine the source-area geochronology and source sedimentary basin thermal histories, and ultimately the timing of multiple tectonothermal events in the Central Andes. Apatite triple dating of samples from the Eocene Geste Formation in the Salar de Pastos Grandes basin shows late Precambrian-Devonian apatite U-Pb crystallization ages, Eocene apatite fission track (AFT), and Eocene-Miocene (U-Th)/He (ca. 8-47 Ma) cooling ages. Double dating of cobbles from equivalent strata in the Arizaro basin documents early Eocene (46.2 +/- 3.9 Ma) and Cretaceous (107.6 +/- 7.6, 109.5 +/- 7.7 Ma) AFT and Eocene-Oligocene (ca. 55-30 Ma) (U-Th)/He ages. Thermal modeling suggests relatively rapid cooling between ca. 80 and 50 Ma and reheating and subsequent diachronous basin exhumation between ca. 30 Ma and 5 Ma. The Ar-40/Ar-39 white mica ages from the same samples in the Salar de Pastos Grandes area are mainly 400-350 Ma, younger than apatite U-Pb ages, suggesting source- terrane cooling and exhumation during the Devonian-early Carboniferous. Together these data reveal multiple phases of mountain building in the Paleozoic and Cenozoic. Basin burial temperatures within the plateau were limited to <80 degrees C and incision occurred diachronously during the Cenozoic.}, language = {en} } @article{VasquezAltenbergerRomeretal.2010, author = {Vasquez, M{\´o}nica and Altenberger, Uwe and Romer, Rolf L. and Sudo, Masafumi and Moreno-Murillo, Juan Manuel}, title = {Magmatic evolution of the Andean Eastern Cordillera of Colombia during the Cretaceous : Influence of previous tectonic processes}, issn = {0895-9811}, doi = {10.1016/j.jsames.2009.02.003}, year = {2010}, abstract = {The Eastern Cordillera of the Colombian Andes represents an inverted Cretaceous basin where Cretaceous magmatism is characterized by rare mafic dykes and sills. We use Ar-40/Ar-39, Sr-Nd-Pb isotopes, as well as major and trace elements analyses of Cretaceous intrusions from both flanks of the Eastern Cordillera in combination with structural data to document the complex evolution of the basin. Magmatism, which is diachronous and geochemically diverse, seems to be related to mantle melting beneath the most subsiding segments of each sub-basin during enhanced extensional tectonics. The mafic intrusions display two different compositional series: an alkaline one with OIB-like pattern and a tholeiitic one with MORB-like features. This indicates at least two diverse mantle sources. Trace-element patterns suggest that the intrusions were emplaced in an extensional setting. Ar-40/Ar-39 dating on primary plagioclase and hornblende provides plateau ages between similar to 136 and similar to 74 Ma. The geochemical and temporal diversities show that the emplacement of the magmas was tectonically controlled, each sub-basin reflecting an individual subsidence event.}, language = {en} } @article{OzawaTagamiListancoetal.2004, author = {Ozawa, Ayako and Tagami, Takahiro and Listanco, Eddie L. and Arpa, Carmencita B. and Sudo, Masafumi}, title = {Initiation and propagation of subduction along the Philippine Trench : evidence from the temporal and spatial distribution of volcanoes}, issn = {1367-9120}, year = {2004}, abstract = {K-Ar ages of 37 samples collected from the Bicol peninsula, the Luzon island, Philippines, were determined by the unspiked sensitivity method in order to constrain the timing of initiation of subduction along the Philippine Trench. The measured K-Ar ages range from 0 to 7 Ma with two old outliers of 27 and 43 Ma. Together with K-Ar ages previously reported on volcanics in Leyte and eastern Mindanao, subduction volcanism has likely propagated from north to south: similar to 6.6 Ma in Bicol and similar to 3.5 Ma in Leyte and its vicinity. The temporal and spatial distribution suggests that the subduction volcanism started earlier in the north than in the south. This is consistent with the southern propagation of subduction along the Philippine Trench from similar to 8 Ma. (C) 2003 Elsevier Ltd. All rights reserved}, language = {en} } @article{OzawaTagamiSudo2004, author = {Ozawa, Ayako and Tagami, T. and Sudo, Masafumi}, title = {K-Ar geochronology of the temporal change of eruptive style in the eastern Izu peninsula, central Japan}, issn = {1038-4871}, year = {2004}, abstract = {A recent K-Ar study elucidated that eruptive style in the eastern Izu peninsula changed from polygenetic to monogenetic volcano at 0.3-0.2 Ma. To narrow down the time of change, we determined 10 K-Ar ages on Togasayama Andesite of Amagi volcano, the youngest polygenetic volcano in the area, and Togasayama Monogenetic Volcano, one of the oldest monogenetic volcanoes in the area, which overlies a part of the Togasayama Andesite. Dating results showed that the Togasayama Andesite effused at least from 0.34 to 0.20 Ma, whereas the Togasayama Monogenetic Volcano erupted at 0.26- 0.29 Ma, suggesting that the northern part of the Togasayama Andesite effused after the eruption of the Togasayama Monogenetic Volcano. Considering previous data, it is therefore inferred that change of eruptive style in the eastern Izu area occurred during the period 0.29-0.20 Ma, with considerable overlap of both polygenetic and monogenetic volcanism}, language = {en} } @misc{PourteauSudoCandanetal.2013, author = {Pourteau, Amaury and Sudo, Masafumi and Candan, Osman and Lanari, P. and Vidal, O. and Oberh{\"a}nsli, Roland}, title = {Neotethys closure history of Anatolia - insights from Ar-40-Ar-39 geochronology and P-T estimation in high-pressure metasedimentary rocks}, series = {Journal of metamorphic geology}, volume = {31}, journal = {Journal of metamorphic geology}, number = {6}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0263-4929}, doi = {10.1111/jmg.12034}, pages = {585 -- 606}, year = {2013}, abstract = {The multiple high-pressure (HP), low-temperature (LT) metamorphic units of Western and Central Anatolia offer a great opportunity to investigate the subduction-and continental accretion-related evolution of the eastern limb of the long-lived Aegean subduction system. Recent reports of the HP-LT index mineral Fe-Mg-carpholite in three metasedimentary units of the Gondwana-derived Anatolide-Tauride continental block (namely the Afyon Zone, the Oren Unit and the southern Menderes Massif) suggest a more complicated scenario than the single-continental accretion model generally put forward in previous studies. This study presents the first isotopic dates (white mica Ar-40-Ar-39 geochronology), and where possible are combined with P-T estimates (chlorite thermometry, phengite barometry, multi-equilibrium thermobarometry), on carpholite-bearing rocks from these three HP-LT metasedimentary units. It is shown that, in the Afyon Zone, carpholite-bearing assemblages were retrogressed through greenschist-facies conditions at c. 67-62 Ma. Early retrograde stages in the Oren Unit are dated to 63-59 Ma. In the Kurudere-Nebiler Unit (HP Mesozoic cover of the southern Menderes Massif), HP retrograde stages are dated to c. 45 Ma, and post-collisional cooling to c. 26 Ma. These new results support that the Oren Unit represents the westernmost continuation of the Afyon Zone, whereas the Kurudere-Nebiler Unit correlates with the Cycladic Blueschist Unit of the Aegean Domain. In Western Anatolia, three successive HP-LT metamorphic belts thus formed: the northernmost Tavsanli Zone (c. 88-82 Ma), the Oren-Afyon Zone (between 70 and 65 Ma), and the Kurudere-Nebiler Unit (c. 52-45 Ma). The southward younging trend of the HP-LT metamorphism from the upper and internal to the deeper and more external structural units, as in the Aegean Domain, points to the persistence of subduction in Western Anatolia between 93-90 and c. 35 Ma. After the accretion of the Menderes-Tauride terrane, in Eocene times, subduction stopped, leading to continental collision and associated Barrovian-type metamorphism. Because, by contrast, the Aegean subduction did remain active due to slab roll-back and trench migration, the eastern limb (below Southwestern Anatolia) of the Hellenic slab was dramatically curved and consequently teared. It therefore is suggested that the possibility for subduction to continue after the accretion of buoyant (e.g. continental) terranes probably depends much on palaeogeography.}, language = {en} } @article{WillnerMassonneRingetal.2012, author = {Willner, Arne P. and Massonne, Hans-Joachim and Ring, Uwe and Sudo, Masafumi and Thomson, Stuart N.}, title = {P-T evolution and timing of a late Palaeozoic fore-arc system and its heterogeneous Mesozoic overprint in north-central Chile (latitudes 31-32 degrees S)}, series = {Geological magazine}, volume = {149}, journal = {Geological magazine}, number = {2}, publisher = {Cambridge Univ. Press}, address = {New York}, issn = {0016-7568}, doi = {10.1017/S0016756811000641}, pages = {177 -- 207}, year = {2012}, abstract = {In the late Palaeozoic fore-arc system of north-central Chile at latitudes 31-32 degrees S (from the west to the east) three lithotectonic units are telescoped within a short distance by a Mesozoic strikeslip event (derived peak P-T conditions in brackets): (1) the basally accreted Choapa Metamorphic Complex (CMC; 350-430 degrees C, 6-9 kbar), (2) the frontally accreted Arrayan Formation (AF; 280-320 degrees C, 4-6 kbar) and (3) the retrowedge basin of the Huentelauquen Formation (HF; 280-320 degrees C, 3-4 kbar). In the CMC, Ar-Ar spot ages locally date white-mica formation at peak P-T conditions and during early exhumation at 279-242 Ma. In a local garnet mica-schist intercalation (570-585 degrees C, 11-13 kbar) Ar-Ar spot ages refer to the ascent from the subduction channel at 307-274 Ma. Portions of the CMC were isobarically heated to 510-580 degrees C at 6.6-8.5 kbar. The age of peak P-T conditions in the AF can only vaguely be approximated at >= 310 Ma by relict fission-track ages consistent with the observation that frontal accretion occurred prior to basal accretion. Zircon fission-track dating indicates cooling below similar to 280 degrees C at similar to 248 Ma in the CMC and the AF, when a regional unconformity also formed. Ar-Ar white-mica spot ages in parts of the CMC and within the entire AF and HF point to heterogeneous resetting during Mesozoic extensional and shortening events at similar to 245-240 Ma, similar to 210-200 Ma, similar to 174-159 Ma and similar to 142-127 Ma. The zircon fission-track ages are locally reset at 109-96 Ma. All resetting of Ar-Ar white-mica ages is proposed to have occurred by in situ dissolution/precipitation at low temperature in the presence of locally penetrating hydrous fluids. Hence syn-and postaccretionary events in the fore-arc system can still be distinguished and dated in spite of its complex heterogeneous postaccretional overprint.}, language = {en} }